bpo-40275: Use new test.support helper submodules in tests (GH-21743)

diff --git a/Lib/test/test_socketserver.py b/Lib/test/test_socketserver.py
index 5db8cec..7cdd115 100644
--- a/Lib/test/test_socketserver.py
+++ b/Lib/test/test_socketserver.py
@@ -15,6 +15,7 @@
 
 import test.support
 from test.support import reap_children, verbose
+from test.support import os_helper
 from test.support import socket_helper
 from test.support import threading_helper
 
@@ -299,7 +300,7 @@
     KeyboardInterrupt are not passed."""
 
     def tearDown(self):
-        test.support.unlink(test.support.TESTFN)
+        os_helper.unlink(os_helper.TESTFN)
 
     def test_sync_handled(self):
         BaseErrorTestServer(ValueError)
@@ -329,7 +330,7 @@
         self.check_result(handled=False)
 
     def check_result(self, handled):
-        with open(test.support.TESTFN) as log:
+        with open(os_helper.TESTFN) as log:
             expected = 'Handler called\n' + 'Error handled\n' * handled
             self.assertEqual(log.read(), expected)
 
@@ -347,7 +348,7 @@
         self.wait_done()
 
     def handle_error(self, request, client_address):
-        with open(test.support.TESTFN, 'a') as log:
+        with open(os_helper.TESTFN, 'a') as log:
             log.write('Error handled\n')
 
     def wait_done(self):
@@ -356,7 +357,7 @@
 
 class BadHandler(socketserver.BaseRequestHandler):
     def handle(self):
-        with open(test.support.TESTFN, 'a') as log:
+        with open(os_helper.TESTFN, 'a') as log:
             log.write('Handler called\n')
         raise self.server.exception('Test error')